The Electronic Frontier Foundation on Thursday published a disturbing report about South Carolina’s brutal crackdown on the use of social-media networks by the state’s prison inmates.

Based on information obtained through South Carolina’s Freedom of Information Act request system, E.F.F. identified hundreds of cases in which inmates have been punished with solitary confinement for posting online (usually on Facebook). That’s already unsettling, but the details are even worse: “In 16 cases, inmates were sentenced to more than a decade in what’s called disciplinary detention, with at least one inmate receiving more than 37 years in isolation.”

As E.F.F. explains, the Southern Carolina Department of Corrections considers posting on social media a Level One offense—requiring punishments equivalent to those meted out after inmates commit violent acts, including murder, rioting, escape, and rape.

Some inmates share their log-in info with family members who post from outside of the prison. Others use cell phones, which are snuck into prisons. The S.C.D.C. has made it easy for citizens to report inmate social-media usage, plastering a large button on their Web site and encouraging folks to turn in seemingly illicit profiles. E.F.F.’s reporting also appears to show Facebook enforcing prison guidelines that go beyond the scope of the social network’s terms of service, a charge the company has denied. (For more on the type of postings that make it out from inside prisons, read Fusion’s great look at what journalists Kevin Roose and Pendarvis Harshaw termed “the prison system’s illicit digital world,” and check out the Vine and Facebook updates posted from the inside.)

The most striking cases of solitary-for-Facebook punishments that E.F.F. found are almost difficult to comprehend. One inmate, Tyheem Henry, was sentenced to 37.5 years, and stripped of 74 years worth of what the E.F.F. describes as “telephone, visitation, and canteen privileges.” His crime? Thirty-eight Facebook posts.

Walter Brown, another South Carolina inmate who used Facebook (35 posts) received 34.5 years in solitary, and lost his communication and canteen privileges for 69 years. In May of last year, Jonathan McClain received 24.6 years of solitary, and was stripped of the same privileges for 49 years, all over 25 posts.

E.F.F. has posted a list of demands for Facebook. The organization, a nonprofit that works on issues such as digital privacy and security, wants Facebook to stop taking down inmate accounts unless a serious breach of Facebook’s terms of service is identified. E.F.F. believes inmate postings have “public value,” and can help shed light on abuses within the system. (Abuses within the prison system are rampant; for an illustrative example, read the report U.S. attorney Preet Bharara’s office released after investigating the horrors visited upon young inmates at New york City’s Rikers Island facility.) E.F.F. also asks that Facebook increase transparency in interactions with corrections departments.

South Carolina is notable for the sheer volume of cases—there have been 432 disciplinary cases since the state’s policy made using social media a Level One offense in 2012—but other states are also putting inmates in solitary for online activity. E.F.F. points to a case in New Mexico wherein an inmate was sentenced to 60 days in solitary after relatives logged into his Facebook account, and to a new law in Alabama that makes posting on behalf of an inmate a misdemeanor. Similar laws and disciplinary policies have come under harsh legal review, with some departments and states either voluntarily or forcibly repealing similarly aggressive directives.